OFFSET
1,1
COMMENTS
Is this sequence infinite?
All the terms are Fermat pseudoprimes to base 2 (A001567). For a proof see, e.g., Jaroma and Reddy (2007). - Amiram Eldar, Jul 24 2021
LINKS
Giuseppe Coppoletta, Table of n, a(n) for n = 1..7
John H. Jaroma and Kamaliya N. Reddy, Classical and alternative approaches to the Mersenne and Fermat numbers, The American Mathematical Monthly, Vol. 114, No. 8 (2007), pp. 677-687.
Samuel S. Wagstaff, The Cunningham Project, Complete factoring status (compiled by Wilfrid Keller).
PROG
(PARI) a152155(n) = centerlift(Mod(3, 2^(2^n)+1)^(2^(2^n-1)))
terms(n) = my(i=0, k=1); while(1, if(a152155(k)!=-1, print1(2^(2^k)+1, ", "); i++); if(i==n, break); k++)
terms(4) \\ print initial 4 terms
CROSSREFS
KEYWORD
nonn
AUTHOR
Felix Fröhlich, Jan 24 2017
STATUS
approved